Pixar Animation has removed the director of its 2014 film, "The Good Dinosaur," and not named a replacement, marking the fourth time in eight movies that the Emeryville studio has made a director change midstream.

With the film's release date fast approaching and various creative choices unmade, Pixar executives decided to replace director Bob Peterson this summer, according to the studio's president, Ed Catmull.

"All directors get really deep in their films," Catmull said this week. "Sometimes you just need a different perspective to get the idea out. Sometimes directors ... are so deeply embedded in their ideas it actually takes someone else to finish it up. I would go so far as to argue that a lot of live-action films would be better off with that same process."

Peterson, who began at Pixar as an animator on its first feature film, "Toy Story," and co-directed the 2009 Oscar-winning movie "Up," conceived the idea for "The Good Dinosaur," which envisions an Earth where dinosaurs never became extinct.

Until a new director is named, Pixar is relying on a team of people to shepherd various sections of the movie, due in theaters in nine months. That group includes Pixar Chief Creative Officer John Lasseter, "Toy Story 3" director Lee Unkrich, "Brave" director Mark Andrews and the film's original co-director Peter Sohn (at Pixar, a co-director plays a deputy role to the director).

The move comes as Pixar is under mounting pressure to build on its early successes in an increasingly competitive marketplace; this year will see the wide theatrical release of 11 animated movies, up from six a decade ago.

The studio has changed directors on three other films — Brad Bird replaced Jan Pinkava on the 2007 movie "Ratatouille," Lasseter replaced Brad Lewis on 2011's "Cars 2" and Andrews replaced Brenda Chapman on 2012's "Brave." Each of those movies went on to gross more than $500 million at the box office worldwide, and "Brave" and "Ratatouille" won Oscars for animated feature, but "Cars 2" was the rare critical disappointment.

Over its 14 feature films produced since 1995, the computer animation studio has enjoyed outsized artistic and commercial success, but in recent years critics have suggested that it is in a creatively fallow period.

Pixar's 2013 film, the comedy "Monsters University" from first-time feature director Dan Scanlon, just became the fourth Pixar film to pass $700 million at the global box office, finding a large audience despite comparatively moderate reviews.

In the world of live-action films, changing a director when a film is already in production is rare, though it happened this year on the independent western "Jane Got a Gun," when Gavin O'Connor replaced director Lynne Ramsay after she failed to show up on the first day of shooting in New Mexico.

Animated films tend to have much longer schedules than live-action ones, with story changes often occurring after production has begun. As a result, personnel changes are far more common — Genndy Tartakovsky, who helmed last year's Sony Pictures Animation hit "Hotel Transylvania," was the sixth director to work on that film.

Leading an animated movie combines skills that can be hard to find in one person — the imagination to conceive an original idea and the command to manage crews of 200 to 300 people operating on budgets north of $200 million.

"Up" director Pete Docter in June said the method of choosing directors at Pixar is imperfect.

"We take our best guess," said Docter, whose next movie, "Inside Out," is due in 2015. "We try to diagnose: What are the necessary skills? How does this person measure up? They're going to need buttressing here, here they totally shine, and try to pair them with the right people. But if you figure it out, let us know."

Industry watchers started to speculate about Peterson's status when he didn't attend D23, Disney's fan conference in Anaheim this month, to showcase footage from "The Good Dinosaur." Instead, Sohn and producer Denise Ream represented the film, introducing its premise of a 70-foot-tall teenage dinosaur who befriends a young human boy.

Ream too represents a change on the film. The "Cars 2" producer has stepped in to replace John Walker, who left to work on "Tomorrowland," Bird's upcoming live action film for Disney, which owns Pixar.

Peterson, still employed at Pixar, declined to comment for this story. He has another directing project in development, according to Jim Morris, general manager and executive vice president of production for Pixar. "Bob is still working at the studio, and we hope he will stay here for the rest of his natural life," Morris said.

As of now, the release date for "The Good Dinosaur" is unchanged and the movie is proceeding on its production schedule, according to Catmull. "We've been around long enough to know it will never be smooth," Catmull said. "But getting this process smooth is not our goal; our goal is to make the movie great."

For the last two years, perhaps the most mystery-shrouded project at Pixar Animation has been the next film by "Monster's Inc." and "Up" director Pete Docter, a story set inside the brain of a young girl.

John Lasseter's colorful wardrobe aside, there are two eye-popping things about the golden age of Pixar, an era that started with the release of "Toy Story" in 1995 and, depending on how you view it, either ended in 2011 or is still going.